1. Field of the Invention
The present invention relates to a portable bag in which fragile articles such as cameras and camera components can be stored and carried in a safe manner, and particularly, to a portable bag in which the articles stored inside are protected from external impact.
2. Background Art
Generally, portable bags for storing and carrying expensive and impact-sensitive articles such as cameras and measuring instruments are rectangular and hexahedral in shape. Inside of each panel, a sponge sheet is inserted such that the sponge sheet serves to maintain the rectangular and hexahedral shape of the portable bag, as well as to protect the articles stored inside of the bag from external impact.
However, it is difficult to manufacture portable bags having sponge sheets of the necessary strength and elasticity without encountering many disadvantages. For example, when the outer and inner layers are sewn together after inserting sponge sheets between the outer layers and the inner layers, even a heavy duty sewing machine is overworked due to the thickness and strength of the sponge sheet. Consequently, the quality of the sewing becomes unacceptable, in that it is very difficult to properly finish the edge portions or sew the seams in a straight line. Thus, the aesthetic appearance of the bag is degraded and the walls of the bag become twisted.
When the walls in which the sponge sheets are inserted are joined together, the inside of the bag must be sewn up. Therefore, the bag must be sewn with the inside out, while the finishing sewing is done with the bag right side out. In this case, turning the bag from the inside to the right side out is not easy because of the resilency and strength of the sponge. Thus, the manufacturing steps, i.e. insertion of the sponge sheets, the sewing, turning the bag inside and right side out and the finishing work are all difficult tasks, resulting in an excessive expenditure of time and labor, thereby increasing the overall manufacturing cost of the bag.
In some conventional bags, sponge sheets are selected having the necessary strength (other than the ordinary flexible ones); however, in such a case, if a great external impact is applied, the sponge sheets are deformed, thereby making it impossible to effectively protect the stored articles. Such problems are not only attributed to the insufficiency of the strength of the sponge sheets, but also to the fact that there is no rigid member between the outer and inner layers.